合并共享公共元素的列表 [英] Merge lists that share common elements

问题描述

我的输入是一个列表列表.其中一些共享相同的元素，例如.

My input is a list of lists. Some of them share common elements, eg.

L = [['a','b','c'],['b','d','e'],['k'],['o','p'],['e','f'],['p','a'],['d','g']]

我需要合并所有共享一个公共元素的列表，只要没有更多列表具有相同的项目，就重复此过程.我想过使用布尔运算和 while 循环，但没有想出一个好的解决方案.

I need to merge all lists, that share a common element, and repeat this procedure as long as there are no more lists with the same item. I thought about using boolean operations and a while loop, but couldn't come up with a good solution.

最终结果应该是:

L = [['a','b','c','d','e','f','g','o','p'],['k']] 

推荐答案

您可以将列表视为图形的符号，即 ['a','b','c']是一个有 3 个节点相互连接的图.您要解决的问题是找到该图中的连通分量.

You can see your list as a notation for a Graph, ie ['a','b','c'] is a graph with 3 nodes connected to each other. The problem you are trying to solve is finding connected components in this graph.

您可以为此使用 NetworkX，其优点是几乎可以保证正确:

You can use NetworkX for this, which has the advantage that it's pretty much guaranteed to be correct:

l = [['a','b','c'],['b','d','e'],['k'],['o','p'],['e','f'],['p','a'],['d','g']]

import networkx 
from networkx.algorithms.components.connected import connected_components


def to_graph(l):
    G = networkx.Graph()
    for part in l:
        # each sublist is a bunch of nodes
        G.add_nodes_from(part)
        # it also imlies a number of edges:
        G.add_edges_from(to_edges(part))
    return G

def to_edges(l):
    """ 
        treat `l` as a Graph and returns it's edges 
        to_edges(['a','b','c','d']) -> [(a,b), (b,c),(c,d)]
    """
    it = iter(l)
    last = next(it)

    for current in it:
        yield last, current
        last = current    

G = to_graph(l)
print connected_components(G)
# prints [['a', 'c', 'b', 'e', 'd', 'g', 'f', 'o', 'p'], ['k']]

为了自己有效地解决这个问题，无论如何你必须将列表转换成图形化的东西，所以你最好从一开始就使用 networkX.

To solve this efficiently yourself you have to convert the list into something graph-ish anyways, so you might as well use networkX from the start.

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